The NFL season kicked off with great excitement on Thursday, as American football fans across the United States tuned in to watch the New England Patriots - the 2017 Super Bowl winners - suffer a shock defeat to the Kansas City Chiefs.

Yet, the build-up to the NFL season has been focused on a man who has found himself out of the league: Colin Kaepernick.

In August 2016, the San Francisco 49ers quarterback staged a silent protest when he refused to stand for the national anthem before an NFL game, protesting about police killings of unarmed black men in a country that "oppresses black people and people of colour".

The issue has divided opinion in the US, and Kaepernick has faced a barrage of abuse and criticism, including a comment from then-US presidential hopeful Donald Trump who, brushing aside the issue of racism, told him to "find a country that works better for him".

Yet, many have also come to his defence, including fellow athletes and civil rights activists, while growing numbers of US professional athletes have also decided to "take a knee" during the national anthem at the start of games.

Online, many social media users are using the #ImwithKap hashtag, saying they will boycott the NFL until Kaepernick is picked up by a club.

Kaepernick's protest stirred a heated debate in the US, but also resonated internationally.

Inspired by Kaepernick's protest, Khalid Albaih, a Qatar-based Sudanese political cartoonist whose creations have been shown in exhibitions around the world, created an illustration showing the quarterback kneeling with his afro in the shape of a massive black fist.

Albaih's cartoon has since gone viral on social media - it has also been printed on T-shirts worn by many activists, sports fans and celebrities - sparking a lot of discussions about racism in the US.

Here, in his own words, Albaih explains to Al Jazeera the story behind the cartoon, his motivation and the reason for its popularity.

POLITICAL CARTOONIST KHALID ALBAIH:

I did the cartoon exactly a year ago, when I was in the US teaching a course in human rights. I don't know anything about American football, but I was reading the news and saw the image of Colin Kaepernick kneeling down.

A year prior to that, I did a short documentary with an artists' collective that I work with called CULTURUNNERS. The documentary was called "We the People" and it was basically a connection about civil rights and human rights.

For us, as artists coming in from the Arab Spring generation, the civil rights movement [in the US] worked - after all, there was a blacked president.

So we wanted to study what happened during the civil rights movement, and we toured the US. We went and visited the Malcolm X memorial and several other cities and met with black activists and had a lot of conversations about that.

So, when I saw the photograph of Kaepernick kneeling down and I read the articles and everything that was happening, this struck me in exactly the same way like the image of [Olympic sprinters Tommie Smith and John Carlos] lifting their fists in the 1968 Olympics.

It's the same powerful stand-up for an athlete - it created a lot of confusion, a lot of polarising and a lot of people talking about it.

[It resonated strongly among people] because it's really about what was happening at the time - him saying that at a time when police violence and racial violence is at a high in the US, and now this is getting a lot of attention because of social media.

It just really reminded a lot of people that the civil rights movement didn't end. It's still continuing and this is a huge part of it as well.